The U.S. Pat. Nos. 4,110,185 and 4,274,932, to Williams et al., the relevant disclosures of which are incorporated herein by reference, disclose the use of substantially crystalline polypropylene as a material of construction for radiation sterilizable articles such as syringes, tube assemblies, tissue culture flasks, packaging film, and the like. However, when polypropylene is subjected to high energy radiation such as, for example, gamma rays (from cobalt 60), high energy electrons and x-rays, to sterilize articles made therefrom, the material tends to degrade. The two patents not only disclose this problem, but propose solutions to it. The first patent teaches the use of an additive termed a mobilizer, such as a hydrocarbon oil, while the second patent teaches in addition to the mobilizer, the use of polypropylene which has been treated to give it a narrow molecular weight distribution. Application of these teachings of the two patents does inhibit the onset of embrittlement of high energy radiated polypropylene, but further improvement is needed.
This invention provides such improvement.